Eli5 How are ball bearings made precisely spherical?



So the ‘ball’ part of the bearings must have to be perfectly smooth and of uniform size to work correctly, right? So how does the manufacturing process ensure precise dimensions across all 3 axes with perfect repeatability? Also what addition complexities would arise if we take into account bearings from decades ago when the manufacturing process would not have the benefits of modern electronics?

In: Engineering


They begin as round-ish rough pieces that are cut from raw steel stock. These pieces are rolled into a spherical shape in much the same way that you’d roll a ball of plasticine between your hands, except that the surfaces they’re rolled between are very hard. For more precise bearings there are additional rolling operations, each one more precise than the last.

I don’t expect that electronics alters the process much, except that it probably makes the inspection and measurement stages faster.